Tetramorium bessonii Forel, 1891

Garcia, Francisco Hita & Fisher, Brian L., 2012, The ant genus Tetramorium Mayr (Hymenoptera: Formicidae) in the Malagasy region — taxonomy of the T. bessonii, T. bonibony, T. dysalum, T. marginatum, T. tsingy, and T. weitzeckeri species groups, Zootaxa 3365, pp. 1-123 : 15-17

Tetramorium bessonii Forel, 1891

(figs 4, 5, 14, 15, 16)

Tetramorium (Xiphomyrmex) bessonii Forel, 1891:156 . Syntype workers, MADAGASCAR, Fianarantsoa, Pays des Betsileo (Besson) (BMNH: CASENT0102347; MHNG: CASENT0101277, CASENT0101278, CASENT0101297, CASENT0101298; NMHB: CASENT0101145) [examined]. [Combination in Xiphomyrmex by Wheeler, W.M. 1922:1031; in Tetramorium by Bolton, 1979:141].

Diagnosis

Tetramorium bessonii can be easily distinguished from other species of the group by the following character set: head distinctly longer than wide (CI 92–96); petiolar node squamiform and strongly anteroposteriorly compressed with anterodorsal margin situated higher than posterodorsal margin, dorsum tapering backwards posteriorly, in dorsal view strongly transverse (DPeI 209–270).

Description

HL 0.61–0.88 (0.81); HW 0.58–0.83 (0.76); SL 0.44–0.62 (0.58); EL 0.14–0.19 (0.17); PH 0.38–0.49 (0.45); PW 0.47–0.63 (0.58); WL 0.83–1.11 (1.03); PSL 0.17–0.26 (0.23); PTL 0.10–0.14 (0.12); PTH 0.29–0.38 (0.34); PTW 0.23–0.30 (0.27); PPL 0.21–0.29 (0.26); PPH 0.27–0.37 (0.32); PPW 0.27–0.38 (0.35); CI 92–96 (94); SI 73–78 (76); OI 21–23 (23); LMI 54–60 (57); DMI 54–60 (57); PSLI 27–30 (28); PeNI 42–50 (47); LPeI 29–39 (34); DPeI 209–270 (237); PpNI 57–64 (60); LPpI 77–84 (80); DPpI 123–146 (135); PPI 117–135 (127) (15 measured).

Head distinctly longer than wide (CI 92–96). Anterior clypeal margin with distinct median impression. Frontal carinae well-developed, ending shortly before posterior head margin. Antennal scrobes faint and weakly developed, posterior and ventral margins never differentiated. Antennal scapes relatively short, not reaching posterior head margin (SI 73–78). Eyes small to moderate (OI 21–23). Mesosomal outline in profile convex, dorsally transversely rounded, weakly to moderately marginate from lateral to dorsal mesosoma, promesonotal suture generally absent, sometimes present but shallow, metanotal groove weakly developed to absent; mesosoma comparatively stout and high (LMI 54–60). Propodeal spines elongate-triangular to spinose, long, and acute (PSLI 27–30); propodeal lobes very small and broadly triangular. Petiolar node strongly squamiform and anteroposteriorly compressed, anterior and posterior faces not parallel, anterodorsal margin higher situated and better developed than weaker posterodorsal margin, dorsum tapering backwards posteriorly; node in dorsal view transverse, between 2.1 to 2.7 times wider than long (DPeI 209–270), in lateral view more than 2.5 times higher than long (LPeI 29–39). Postpetiole in profile rounded and weakly anteroposteriorly compressed, approximately 1.2 to 1.3 times higher than long (LPpI 77–84), in dorsal view approximately 1.3 to 1.4 times wider than long (DPpI 123–146). Postpetiole in profile more voluminous than petiolar node, in dorsal view approximately 1.2 to 1.3 times wider than petiolar node (PPI 117–135). Mandibles generally striate, sometimes weakly sculptured; clypeus always with strong median longitudinal ruga and one or two weaker rugae at each side; cephalic dorsum between frontal carinae with one well-developed longitudinal median ruga and several irregular longitudinal rugae laterally, median ruga diverging approximately at eye level into two rugae running to posterior clypeal margin, rugae fading out shortly before posterior head margin, median ruga of same length as frontal carinae; scrobal area, lateral and ventral head mostly with irregular longitudinal rugulae. Head with faint punctate ground sculpture. Mesosomal dorsum generally unsculptured, rarely with faint traces of rugulae anteriorly, lateral mesosoma anteriorly almost unsculptured, posteriorly irregularly, longitudinally rugulose. Waist segments and gaster unsculptured and smooth. Mesosoma, waist segments, and first gastral tergite moderately shining due to faint punctate or foveolate ground sculpture. All dorsal surfaces of body generally with numerous fine, long, decumbent to erect hairs, and comparatively long appressed to subdecumbent pubescence. Colouration mostly of uniform brownish colour, sometimes gaster darker, often head, legs, and gaster much darker brown than mesosoma and waist segments.

Notes

Tetramorium bessonii is a fairly common species in many arid environments in Madagascar. It can be found in the southeastern and southwestern portions of the island, though it seems completely absent from the southern tip. From these southern localities northwards it is also commonly encountered on the High Plateau, especially in the area around Antananarivo and Moramanga. In the northern part of Madagascar, however, T. bessonii seems to be comparatively rare since it is only known from few localities. It was mostly sampled from anthropogenically modified and grassland habitats followed by spiny forests, thickets, and tropical dry forests, while it was only seldom found in montane or littoral rainforests. The preferred foraging microhabitat is very likely the ground and lower vegetation, and nests are constructed directly in the ground or under rocks.

Within the species group, T. bessonii is morphologically closer to T. artemis and T. wardi due to approximately the same petiolar node shape, which is squamiform and strongly anteroposteriorly compressed with a highly transverse dorsum. This character separates these three species from the remaining group members, T. malagasy , T. orientale , and T. ryanphelanae , which possess a high nodiform petiolar node with a far less transverse dorsum. However, T. bessonii can be clearly distinguished from T. artemis and T. wardi . The latter both have a head shape that is approximately as long as wide (CI 98–101), whereas the head of T. bessonii is distinctly longer than wide (CI 92–96). Also, T. artemis and T. wardi have relatively short, appressed pubescence on the first gastral tergite, whereas the pubescence is distinctly longer and appressed to decumbent in T. bessonii . Another character that separates the latter species from T. artemis is the sculpture on the cephalic dorsum between the frontal carinae. In T. bessonii one can see a single median ruga and several additional rugae laterally, whereas T. artemis possesses only one median ruga. The sculpture on the cephalic dorsum of T. wardi is similar to that observed in T. bessonii , although it is somewhat less developed. Nevertheless, these species cannot be confused due to the key characters mentioned above.

Material examined

MADAGASCAR: no locality data (Besson); Antananarivo, 18° 55' S, 47° 32' E, 1300 m, 31.I.1993 (P.S. Ward); Antananarivo, Alasora, 18.96245 S, 47.58925 E, 1434 m, grassland, 4.V.2007 (B.L. Fisher et al.); Antananarivo, Alasora, 18.96245 S, 47.58925 E, 1326 m, urban/garden, 4.V.2007 (B.L. Fisher et al.); Antananarivo, Ambohimanga, 18.76125 S, 47.56447 E, 1361 m, roadside, 26.IV.2007 (B.L. Fisher et al.); Antananarivo, Ambatolampy, 19.387 S, 47.4285 E, 1580 m, urban/garden, 30.I.2007 (B.L. Fisher); Antananarivo, Ambatolaona, 18.928 S, 47.88283 E, 1382 m, urban/garden, 19.II.2007 (B.L. Fisher et al.); Antananarivo, 3 km 41° NE Andranomay, 11.5 km 147° SSE Anjozorobe, 18.47333 S, 47.96 E, 1300 m, montane rainforest, 5.-13.XII.2000 (B.L. Fisher, C. Griswold et al.); Antananarivo, Ankazobe, 18.31617 S, 47.11583 E, 1241 m, urban/garden, 9.II.2007 (B.L. Fisher); Antananarivo, Antsahadinta, 19.0128 S, 47.40668 E, 1403 m, urban/garden, 8.V.2007 (B.L. Fisher et al.); Antananarivo, 10 km NE Antananarivo, Lac Alarobie, 18° 45' 32.6'' S, 47° 33' 45.1'' E, 1360 m, 10.III.1991 (G.D. Alpert); Antananarivo, Antsirabe, 19.866 S, 47.0355 E, 1550 m, urban/garden, 5.II.2007 (B.L. Fisher et al.); Antananarivo, Ilafy, 18.85415 S, 47.56575 E, 1385 m, urban/garden, 26.IV.2007 (B.L. Fisher et al.); Antananarivo, Mandoto, 19.57967 S, 46.28967 E, 870 m, urban/garden, 31.I.2007 (B.L. Fisher et al.); Antananarivo, Kaloy, 18.59568 S, 47.65333 E, 1338 m, grassland, 27.IV.2007 (B.L. Fisher et al.); Antsiranana, Ankobahoba, 32.3 km N Ambanja, 13.39166 S, 48.48249 E, 41 m, disturbed littoral rainforest, 12.IV.2008 (B.L. Fisher et al.); Antsiranana, Bekonazy, 5 km W, baobab forest, 23.III.1968 (W.L. Brown); Fianarantsoa, no locality data (Besson); Fianarantsoa, Pays de Betsileo (Besson); Fianarantsoa, Ambalavao, 21.83267 S, 46.93867 E, 1020 m, urban/garden, 13.XII.2006 (B.L. Fisher et al.); Fianarantsoa, 28 km. SSW Ambositra, Ankazomivady, 20.775 S, 47.16833 E, 1670 m, grassland, 9.-13.I.1998 (B.L. Fisher); Fianarantsoa, Imerina (Sikora); Fianarantsoa, Ihosy, 22.40317 S, 46.12917 E, 735 m, urban/garden, 12.XII.2006 (B.L. Fisher); Fianarantsoa, Parc National d'Isalo, Ambovo Springs, 29.3 km 4° N Ranohira, 22.29833 S, 45.35167 E, 990 m, Uapaca woodland, 9.-14.II.2003 (B.L. Fisher, C. Griswold et al.); Fianarantsoa, stream area, 900 m E of Isalo National Park Interpretive Center, 22.62667 S, 45.35817 E, 750 m, open area near stream, 22.I.–2.II.2003 (R. Harin'Hala); Mahajanga, Parc National Tsingy de Bemaraha, 10.6 km ESE 123° Antsalova, 18.70944 S, 44.71817 E, 150 m, tropical dry forest, 16.–20.XI.2001 (B.L. Fisher et al.); Mahajanga, Réserve forestière Beanka, 50.2 km E Maintirano, 18.02649 S, 44.05051 E, 250 m, tropical dry forest, 19.–23.X.2009 (B.L. Fisher et al.); Mahajanga, Réserve forestière Beanka, 50.2 km E Maintirano, 17.88756 S, 44.47265 E, 153 m, tropical dry forest, 31.X.2009 (B.L. Fisher et al.); Mahajanga, Réserve forestière Beanka, 50.7 km E Maintirano, 17.88021 S, 44.46877 E, 140 m, tropical dry forest, 28.X.– 1.XI.2009 (B.L. Fisher et al.); Majunga, Mampikony, 16.09323 S, 47.64278 E, 49 m, urban/garden, 20.III.2007 (B.L. Fisher et al.); Toamasina, Ambatovy, 12.4 km NE Moramanga, 18.85813 S, 48.28488 E, 1040 m, grassland, 4.–8.III.2007 (B.L. Fisher et al.); Toamasina, Moramanga, 18.94417 S, 48.23067 E, 922 m, urban/garden, 14.II.2007 (B.L. Fisher et al.); Toliara, Amboasary, 25.03883 S, 46.3835 E, 25 m, urban/garden, 9.XII.2006 (B.L. Fisher); Toliara, Berenty, Ambosary, 13.VIII.1984 (J.M. Wilson); Toliara, 18 km NNW Betroka, 23° 9' 48'' S, 45° 58' 7'' E, 825 m, savanna, 24.XI.1994 (M.A. Ivie & D.A. Pollock); Toliara, Ejeda, 24.3505 S, 44.516 E, 250 m, urban/garden, 10.XII.2006 (B.L. Fisher); Toliara, Forêt de Beroboka, 5.9 km 131° SE Ankidranoka, 22.23306 S, 43.36633 E, 80 m, tropical dry forest, 12.-16.III.2002 (B.L. Fisher, C. Griswold et al.); Toliara, Forêt de Mahavelo, Isantoria River, 24.75833 S, 46.15717 E, 110 m, spiny forest/thicket, 28.I.–1.II.2002 (B.L. Fisher & C. Griswold); Toliara, Forêt de Tsinjoriaky, 6.2 km 84° E Tsifota, 22.80222 S, 43.42067 E, 70 m, spiny forest/thicket, 6.- 10.III.2002 (B.L. Fisher, C. Griswold et al.); Toliara, Forêt Vohidava 89.2 km N Amboasary, 24.239 S, 46.28233 E, 850 m, tropical dry forest, 8.XII.2006 (B.L. Fisher et al.); Toliara, Ivahona, 23.45591 S, 46.17376 E, 820 m, village/park/garden, 12.II.2009 (B.L. Fisher et al.); Toliara, Malaimbandy, 20.34317 S, 45.59567 E, 180 m, urban/ garden, 2.II.2007 (B.L. Fisher); Toliara, 48 km ENE Morondava, 20° 04' S, 44° 39' E, 30 m, tropical dry forest, 5.I.1991 (D.M. Olson); Toliara, Parc National d'Andohahela, Forêt de Manantalinjo, 33.6 km 63° ENE Amboasary, 7.6 km 99° E Hazofotsy, 24.81694 S, 46.61 E, 150 m, spiny forest/thicket, 12.–16.I.2002 (B.L. Fisher & C. Griswold); Toliara, Parc National d'Andohahela, Forêt d'Ambohibory, 1.7 km 61° ENE Tsimelahy, 36.1 km 308° NW Tolagnaro, 24.93 S, 46.6455 E, 300 m, tropical dry forest, 16.–20.I.2002 (B.L. Fisher & C. Griswold); Toliara, Parc National de Tsimanampetsotsa, Forêt de Bemanateza, 20.7 km 81° E Efoetse, 23.0 km 131° SE Beheloka, 23.99222 S, 43.88067 E, 90 m, spiny forest/thicket, 22.–26.III.2002 (B.L. Fisher et al.); Toliara, Réserve Berenty, 25° 01' S, 46° 18' E, 25 m, tropical dry forest, 9.II.1993 (P.S. Ward); Toliara, Res. Beza Mahafaly, Parcel 1, 23° 39' S, 44° 38' E, 130 m, tropical dry forest, 13.XI.1993 (P.S. Ward); Toliara, Réserve Spéciale Kalambatritra, Ambinanitelo, 23.45707 S, 46.4473 E, 1300 m, grassland, 8.II.2009 (B.L. Fisher et al.); Toliara, Réserve Spéciale Kalambatritra, Ambinanitelo, 23.45373 S, 46.45773 E, 1345 m, grassland, 11.II.2009 (B.L. Fisher et al.); Toliara, Réserve Spéciale Kalambatritra, 23.4185 S, 46.4583 E, 1365 m, grassland, 8.II.2009 (B.L. Fisher et al.); Toliara, Sakaraha, 22.91233 S, 44.53283 E, 470 m, urban/garden, 11.XI.2006 (B.L. Fisher); Toliara, southern IsokyVohimena Forest, 59 km NE Sakaraha, 22.46667 S, 44.85 E, 730 m, tropical dry forest, 21.I.1996 (B.L. Fisher); Tulear Prov., Tulear, near road, Zombitse National Park, 22.8405 S, 44.73117 E, 825 m, spiny deciduous forest, 28.II.–6.III.2002 (R. Harin'Hala).